1. Field of the Invention
The present invention relates to a transfer technique of manufacturing a device formation layer including a semiconductor device composed of a plurality of thin film transistors (hereinafter, TFT).
2. Related Art
In recent years, a technique for forming a TFT using a semiconductor thin film (having a thickness of from approximately several to several hundreds nm) formed over a substrate having an insulating surface has been attracted attention. A TFT is utilized widely for an electronic device such as an IC, an electro-optical device, or the like.
As a substrate for forming these TFTs, a glass substrate or a quartz substrate is widely used now, however, these substrates have some drawbacks such as being fragile and heavy. Further, these substrates are unsuitable for mass-production since it is difficult to use a large-sized glass substrate or a large-sized quartz substrate. Therefore it has been attempted that a device composed of TFTs is formed over a substrate having flexibility as typified by a flexible plastic film.
However, the maximum temperature of the process should be lowered since the heat resistance of a plastic film is low, with the result that a TFT having better electric characteristics than those of a TFT formed over a glass substrate cannot be formed. Thus, a semiconductor device, a display device, or a light-emitting device including a TFT which is directly formed over a substrate has not been realized yet.
At the same time, a technique for forming a thin film device over a glass substrate or a quartz substrate, and peeling the thin film device (transferred body) from the substrate, then transferring to a subject such as a plastic substrate, etc. are disclosed. (For example, Unexamined Patent Publication No. 10-125929)
If a semiconductor device, a display device, or a light-emitting device can be manufactured over a substrate having flexibility such as a plastic film, these devices can be utilized for a display of being thin, lightweight, flexible, and curved, so that the range of application can be broaden out.